Gaseous Emissions and Control in Wastewater Treatment Plants

Gaseous emissions at 14 wastewater treatment plants (WWTPs) were sampled for various manufacturing processes in Taiwan. A large proportion of gaseous pollutants from WWTPs were volatile organic compounds (VOCs). The VOC concentration (ppmv as CH₄) and emission strength (kg CH₄/m³ wastewater) were utilized to identify emission characteristics. Emissions generally declined throughout the treatment process; however, the VOC concentrations exceeded 10,000 ppmv as CH₄ at several closed vessel vents during the primary treatment. The VOC emission strengths, according to the field analysis data, were around 0.000001–0.0068 kg CH₄/m³ wastewater, except two WWTPs with extremely high values of 0.026–0.029 kg CH₄/m³. The current control methods for gaseous emissions from WWTPs were thoroughly evaluated in this study, and resulted in the recommended use of a system of sealed covers, connected by suction to a purification facility, as the optimal technology for controlling VOC emission from WWTPs. Cost analysis results indicate that incinerators with regenerative heat recovery are optimal for treating high VOC concentrations exceeding 10,000 ppmv as CH₄. This study also recommended collecting emissions with wide-ranging concentrations (100–1,000 ppmv as CH₄) from the neutralization and biotreatment stages and then injecting them into the activated sludge basins via blowers.